Method for controlling fluid flow to and from an eye during ophthalmic surgery

ABSTRACT

A method and apparatus provided for controlling fluid control to and from an eye or a phacoemulsification handpiece. The handpiece includes an ultrasonically driven, hollow, sleeved needle and the method includes inserting the needle and sleeve into an eye for phacoemulsification of eye tissue and introducing fluid into the eye through an annulus established between the sleeve and the needle. Aspiration of fragmented tissue and fluid from the eye is conducted through the hollow needle. An initial irrigation fluid pressure is determined and the irrigation fluid flow and aspiration fluid flow are adjusted based upon the initial determination. Thereafter continued determination of irrigation fluid pressure is utilized to continuously adjust irrigation fluid flow and/or aspiration fluid flow.

The present application is a division of U.S. Ser. No. 10/414,950 filedApr. 15, 2003, now pending, which is a division of U.S. Ser. No.09/918,749 filed Jul. 31, 2001, now U.S. Pat. No. 6,579,255.

The present invention generally relates to a method and apparatus forophthalmic surgery. More specifically, the present invention is directedto a method and apparatus for controlling fluid flow to and from an eyeduring ophthalmic surgery.

In retinal and vitreous surgery, a separate needle used to supplyinfusion, or irrigation, fluid or suction, for aspiration, respectively.

Phacoemulsification procedures typically include the use of a handpiecefor inserting a sleeved needle through a corneal incision and thereaftervibrating the needle in order to emulsify hard nuclear material of thecataract lens. The incision is generally made in the region of thelimbus or in the cornea.

An annulus formed between the sleeve and the needle functions as apassage which allows for the introduction, or inflow, of the salinefluid into the eye for irrigation.

The saline fluid prevents the cornea from collapsing as the lensmaterial is emulsified and aspirated. In addition, the saline irrigationfluid aids in the aspiration of emulsified cataract lens material fromthe eye. The aspiration is conducted through the hollow center of thevibrating needle. The handpiece and needle are connected with anexternal power source, an irrigation fluid source, and a vacuum source.A control system provides for coordinated ultrasonic vibration,irrigation and aspiration of fluids to and from the eye.

Heretofore, irrigation fluid pressure has been established through theuse of an elevated bottle, which provides a source of saline solution.It should be appreciated that fluid control and eye pressure are ofutmost importance. Corresponding irrigation and aspiration of flow ratesas hereinabove noted are used to maintained the eye in an inflated,pressurized condition during cataract removal. However, the incisionsize is important since it provides an alternate route for leakage offluid from the eye.

This leakage causes diminished inflation of the eye during cataractsurgery and occurs between the edges of the incision and exteriorsurfaces of sleeved needle. During the phacoemulsification procedure,the needle is manipulated and such manipulation can lead to woundstretching. This, in turn, changes the leakage rate from the eye andcompounds the problem of balanced irrigation and aspiration fluid flowand the maintenance of a proper pressure state of the eye duringsurgery.

Accordingly, variation in wound construction, sleeve/incision geometryand needle size are important as they relate to fluid leakage from thewound. Deflation of the eye, which may be caused by such leakage, maycause certain tissue within the eye to collapse within one another or onthe sleeved needle extending into the eye. In this manner, fluid lossmay cause damage to the cornea, iris, or lens capsule which surround thecataract.

One method for counteracting fluid leakages as to increase the amount ofirrigation and aspiration fluid flow which is inconveniently donethrough raising and lowering of the irrigation source bottle along witha concomitant adjustment in aspiration rate.

Accordingly, there is a need for a system for coordinating irrigationfluid flow and aspiration flow during ophthalmology surgery procedures.The present invention fills that need.

SUMMARY OF THE INVENTION

A method for controlling fluid flow to and from an eye during ophthalmicsurgery includes introducing irrigation fluid into an eye and aspiratingfluid from the eye. During fluid flow initial irrigation fluid pressureis determined. Irrigation fluid flow, aspiration fluid flow and maximumvacuum is adjusted based on the determined initial irrigation fluidpressure. Thereafter irrigation fluid pressure is continuouslydetermined and irrigation fluid flow, aspiration fluid flow and maximumvacuum is continuously adjusted based on the continuous determination ofirrigation fluid pressure.

A handpiece suitable for use in phacoemulsification procedures whileproducing the method of the present invention, generally includes anultrasonically driven, hollow, sleeved needle and the method, inaccordance with the present invention, further includes the steps ofinserting the needle and sleeve into an eye for phacoemulsification ofeye tissue. Irrigation fluid is introduced into the eye through anannulus established between the sleeve and the needle and fluid isaspirated from the eye through the hollow needle.

An initial irrigation fluid pressure is determined and in responsethereto irrigation fluid flow and aspiration fluid flow are adjusted inorder to initially maintain proper eye pressure within the eye.

Thereafter, irrigation pressure is continuously determined and inresponse thereto, the irrigation flow and aspiration fluid flow areadjusted based upon the continuous determination of irrigation fluidpressure. Importantly, the method does not include the raising andlowering of a bottle of irrigation fluid as is necessary in prior artmethods. The present invention is also distinguished from prior artmethod in that the fluid flow rates are automatically regulated, oradjusted based upon irrigation fluid pressure determination. This is tobe distinguished from current method in which control of irrigationfluid is maintained by feedback from a surgeon based upon visualobservation of tissue under the affects of irrigation. In addition, thesurgeon control of irrigation is limited to an on/off control valve andadjustment of the irrigation fluid source height.

In the present invention, the introduction of irrigation fluid into aneye is performed through the use of a positive displacement pump and thestep of adjusting the irrigation fluid flow includes adjusting the pumpspeed.

The determination of irrigation fluid pressure many be done through theuse of a transducer disposed in a line interconnecting the pump andhandpiece or through direct measurement of pressure within the eye.

The adjustment of aspiration fluid flow may include setting a maximumaspiration vacuum pressure as a function of determined irrigation fluidpressure. More particularly, this maximizes aspiration vacuum may be alinear function of the determined irrigation fluid pressure.

The change of irrigation fluid pressure may also be utilized inaccordance with the present invention for providing an indication ofwound leaking.

The apparatus in accordance with the present invention for controllingfluid flow to and from a phacoemulsification handpiece in order toaccommodate changes in incision size and would stretching during eyesurgery generally includes a supply of irrigation fluid and a positivedisplacement pump for introducing irrigation fluid from the supply ofirrigation fluid into an eye through an annulus established between asleeve and a needle of a handpiece.

A vacuum source is provided for aspirating fluid from the eye throughthe hollow portion of the needle and a pressure sensor is provided fordetermining pressure of irrigation fluid introduced into the eye.

A control system is provided for adjusting irrigation fluid and theaspiration fluid flow rates in response to the determined irrigationflow pressure. More particularly, the pressure sensor may be disposed ina line interconnecting the positive displacement pump in the needle or apressure sensor disposed in the eye.

The control system may also include an indication for enablingmonitoring by a surgeon of wound construction consistency based uponirrigation of fluid pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may be more clearly understood with reference tothe following detailed description, in connection with the appendeddrawings, in which:

FIG. 1 is a diagram illustrating apparatus and method in accordance withthe present invention; and

FIG. 2 is a plot of maximum stable vacuum corresponding to measuredirrigation pressure which may be utilized by the control system shown inFIG. 1 for making fluid flow changes.

DETAILED DESCRIPTION

With reference to FIG. 1, there is shown apparatus 10 in accordance withthe present invention for controlling fluid flow to and from aphacoemulsification handpiece 12 which generally includes a supply 14 ofirrigation fluid, a positive displacement pump 16, a vacuum source 18, apressure sensor 20 and a control system 22 described hereinafter ingreater detail and also suitable for performing the method of thepresent invention.

It should be appreciated that while a phacoemulsification handpiece 12is described herein for the practice of the present invention, forillustration purposes, other surgical instruments (not shown) may beutilized for different ophthalmic surgical procedures and separateinfusion and aspiration needles (not shown) may be used for practice ofthe present invention.

The handpiece 12, which may be of any conventional type, includes anultrasonically driven, hollow needle 24 having a sleeve 26 thereaboutwhich establishes an annulus 30 round needle for introducing irrigationfluid into an eye 34 in a conventional manner.

By utilizing the pump 16 which preferably is a positive displacementpump in combination with the pressure sensor 20, a “closed” pressuremeasurement system is provided which enables the precise control ofinfusion pressure into the eye without relying on the height of atraditional irrigation fluid source (not shown). Preferably abi-directional positive displacement pump 16 facilitates precise controlof the fluid pressure.

The control system 22 provides electrical power to the handpiece 12 forultrasonically driving the needle 24 through line 38. Through lines 40,42 the control system 22 controls the pump 16 speed and a vacuum source18 respectively. The aspiration vacuum source 18 may be of anyconventional type and include as, for example, a peristaltic pump. Inputto the control system 22 from the sensor 20 is provided through a line46 or a line 48 from a sensor (not shown) disposed within the eye.

The sensor 20 is disposed in an irrigation line 52 between the pump 16and the handpiece 12. Aspiration from the handpiece 12 and hollow needle24 to the vacuum source 18 occurs through the line 54.

The pressure transducer 20 may be on medical grade compensated sensorpressure which is available from Motorola. Alternatively directirrigation fluid pressure measurement may be made by a transducerdirectly from the eye. A suitable transducer for this mode of operation,is also which is available from Motorola. The control system 20 includessoftware for conducting the function and method of the apparatus ashereinafter described.

A method for controlling fluid flow to and from a phacoemulsificationhandpiece 12 in order accommodate changes in incision size and woundstretching, for example, during eye surgery, generally includes a stepof inserting the needle 24 into the eye for phacoemulsification of eyetissue. Irrigation fluid is introduced into the eye through the annulus30 established between the sleeve 26 and the needle 24. Aspiration ofthe fluid from the eye 34 is then conducted through the hollow needlehandpiece 12 and line 54 to the aspiration vacuum source 18.

An initial irrigation fluid pressure is determined by the sensor 20 andthe irrigation fluid flow from the source 14 is adjusted by the controlsystem 22 through operation of pump 16 based upon a determined initialirrigation fluid pressure as provided by the sensor 20.

Thereafter, the irrigation fluid pressure is continuously determined viathe sensor 20 and the irrigation fluid flow and aspiration fluid flowbased upon this continuous determination of irrigation fluid pressure isprovided by the control system through the lines 40,42 respectively tothe pump 16 aspiration vacuum source 18.

A variation in wound construction, sleeve/incision geometry and needlesize are then mediated by monitoring the pressure present at either thesurgical site or the sensor 20. A leaking wound can be compensated forby adjustment of fluid flow by the control system 22.

It has been found that maximum usable vacuum is a function of irrigationfluid pressure. This relationship is shown in FIG. 2. In FIG. 2, thedata shows a clear trend of increased usable vacuum with an increasedirrigation pressure. This data is derived from various combinations ofsleeves, needles and incision sizes in a laboratory model (not shown).

This relationship can be incorporated as an algorithm in the controlsystem 22 software. Accordingly, the control system 22 can provide amaximum vacuum setting shown on the Y axis on the plot shown on FIG. 1as a basis of a measured irrigation pressure. In addition, the controlsystem 22 may include an indicator 60 which may be visible or audiblefor enabling a surgeon to monitor wound construction consistency basedupon monitoring of irrigation fluid pressure, and changes thereto duringphacoemulsification procedures.

Although there has been hereinabove described a method and apparatus forcontrolling fluid flow to and from an eye or phacoemulsificationhandpiece in accordance with the present invention, for the purpose ofillustrating the manner in which the invention may be used to advantage,it should be appreciated that the invention is not limited thereto.Accordingly, any and all modifications, variations and equivalentarrangement which may occur to those skilled in the art should beconsidered to be within the scope of the present invention as defined inthe appended claims.

1. A method for controlling fluid flow to and from an eye duringophthalmic surgery, said method comprising: introducing irrigation fluidinto an eye; continuously determining irrigation fluid pressure; andusing a change in irrigation fluid pressure to provide an indication ofwound leaking.
 2. A method for controlling fluid flow to and from an eyeduring ophthalmic surgery, said method comprising: introducingirrigation fluid into an eye; determining initial irrigation fluidpressure; adjusting aspiration fluid flow based on the determinedinitial irrigation fluid pressure; continuously determining irrigationfluid pressure after the initial determination; and continuouslyadjusting aspiration fluid flow based on the continuous determination ofirrigation fluid pressure.
 3. The method according to claim 2 whereinthe step of adjusting aspiration fluid flow includes setting a maximumaspiration vacuum pressure as a function of determined irrigation fluidpressure.
 4. The method according to claim 3 wherein the function islinear.
 5. The method according to claim 2 where the step of initiallydetermining irrigation fluid pressure and continuously measuringirrigation fluid pressure includes determining in-line irrigationpressure.